The present invention relates generally to electronically controlled transmission for industrial vehicles and more particularly to an electronically controlled transmission which is operable in two different modes of operation to provide the characteristics of two different transmissions in one transmission.
In the past, industrial vehicles were provided with a transmission having a single operating mode which was a compromise between the transmission conditions required for work situations when the vehicle was being used as designed and for transport situations where the vehicle was being driven from work site to work site.
Generally, in industrial vehicles such as scrapers, a large number of transmission gear ratios at slow speeds are desirable for performing the precision off-highway work functions with torque converter operation available to smooth out transmission shocks due to abrupt loading and unloading of the engine. When the vehicle is driven on-highway for transport between work sites, it is desirable to increase engine efficiency by locking up the energy wasting torque converter and by providing a smaller number of gear ratios to reach highway speeds.
Further, in the past, while either manual or automatic transmissions were available, none provided a hybrid system where some of the transmission ratios were obtained manually while others were obtained automatically, and neither did the systems provide for full manual control as well as manual holding of any automatically selected ratio.